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| United States Patent |
6,165,376
|
|
Miyake
, et al.
|
December 26, 2000
|
Work surface treatment method and work surface treatment apparatus
Abstract
A work is supported by a work support electrode arranged in a vacuum
container, a treatment gas corresponding to intended treatment of the work
is supplied into the container, and a vacuum is produced in the container.
Plasma is formed from the gas by applying an amplitude-modulated
high-frequency power to an electrode electrically insulated from the work
support electrode, said amplitude-modulated high-frequency power being
prepared by effecting amplitude modulation on a basic high-frequency power
having a predetermined frequency in a range from 10 MHz to 200 MHz with a
modulation frequency in a range from 1/1000 to 1/10 of said predetermined
frequency. A positive pulse voltage is applied to the work support
electrode to effect the treatment on the surface of the work supported by
the work support electrode.
| Inventors:
|
Miyake; Koji (Kyoto, JP);
Nakahigashi; Takahiro (Kyoto, JP);
Kuwahara; Hajime (Kyoto, JP)
|
| Assignee:
|
Nissin Electric Co., Ltd. (Kyoto, JP)
|
| Appl. No.:
|
003035 |
| Filed:
|
January 5, 1998 |
Foreign Application Priority Data
| Current U.S. Class: |
216/67; 216/71; 438/729 |
| Intern'l Class: |
H01L 021/00; H05H 001/00 |
| Field of Search: |
216/67,71
438/729
156/345
|
References Cited
U.S. Patent Documents
| 4464223 | Aug., 1984 | Gorin.
| |
| 4764394 | Aug., 1988 | Conrad.
| |
| 4950377 | Aug., 1990 | Huebner.
| |
| 5212425 | May., 1993 | Goebel et al.
| |
| 5698062 | Dec., 1997 | Sakamoto et al. | 156/345.
|
| 5928528 | Jul., 1999 | Kubota et al. | 216/67.
|
| 5997687 | Dec., 1999 | Koshimizu et al. | 156/345.
|
| Foreign Patent Documents |
| 653 501 A1 | May., 1995 | EP.
| |
| 793 254 A2 | Sep., 1997 | EP.
| |
| 0 821 077 A2 | Jan., 1998 | EP.
| |
| 4-26436 | Sep., 1992 | JP.
| |
| 4-280055 | Oct., 1992 | JP.
| |
| 08-255782 | Oct., 1996 | JP.
| |
| 2 240 114 | Jul., 1991 | GB.
| |
Primary Examiner: Dang; Thi
Attorney, Agent or Firm: Arent Fox Kintner Plotkin & Kahn PLLC
Claims
What is claimed is:
1. A work surface treatment method comprising the steps of supporting a
work by a work support electrode arranged in a vacuum container; supplying
a treatment gas corresponding to intended treatment of the work into said
container; forming plasma from said gas by applying in a vacuum an
amplitude-modulated high-frequency power to an electrode electrically
insulated from said work support electrode, said amplitude-modulated
high-frequency power being prepared by effecting amplitude modulation on a
basic high-frequency power having a predetermined frequency in a range
from 10 MHz to 200 MHz with a modulation frequency in a range from 1/1000
to 1/10 of said predetermined frequency; and applying a positive pulse
voltage to said work support electrode to effect the treatment on the
surface of said work supported by said work support electrode.
2. The work surface treatment method according to claim 1, wherein said
amplitude modulation is pulse modulation.
3. The work surface treatment method according to claim 2, wherein the
timing of each rising of said positive pulse voltage is determined between
an intermediate time in the on-period of said pulse-modulated
high-frequency power and a time in the subsequent off-period, and the
timing of each falling of the positive pulse voltage is determined between
a time in the off-period of said pulse-modulated high-frequency power and
an intermediate time in the subsequent on-period.
4. The work surface treatment method according to claim 1, wherein said
positive pulse voltage is in a range from 50 V to 300 kV.
5. The work surface treatment method according to claim 1, wherein a
negative pulse voltage is applied to the work support electrode during the
off-period of application of said positive pulse voltage.
6. The work surface treatment method according to claim 1, wherein said
work has a surface portion made of an electrically insulating material or
carrying a floated potential.
7. A work surface treatment method comprising the steps of supporting a
work by a work support electrode arranged in a vacuum container; supplying
a treatment gas corresponding to intended treatment of the work into said
container; forming plasma from said gas by applying in a vacuum an
pulse-modulated high-frequency power to an electrode electrically
insulated from said work support electrode, said pulse-modulated
high-frequency power being prepared by effecting pulse modulation on a
basic high-frequency power having a predetermined frequency in a range
from 10 MHz to 200 MHz with a modulation frequency in a range from 1/1000
to 1/10 of said predetermined frequency; and applying a positive pulse
voltage in a range from 50 V to 300 kV to said work support electrode to
effect the treatment on the surface of said work supported by said work
support electrode, wherein the timing of rising of said positive pulse
voltage is determined between an intermediate time in the on-period of
said pulse-modulated high-frequency power and a time in the subsequent
off-period, and the timing of falling of the positive pulse voltage is
determined between a time in the off-period of said pulse-modulated
high-frequency power and an intermediate time in the subsequent on-period.
8. The work surface treatment method according to claim 7, wherein a
negative pulse voltage is applied to the work support electrode during the
off-period of application of said positive pulse voltage.
9. The work surface treatment method according to claim 7, wherein said
work has a surface portion made of an electrically insulating material or
carrying a floated potential.
10. The work surface treatment method according to claim 8, wherein said
work has a surface portion made of an electrically insulating material or
carrying a floated potential.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for effecting
treatment on a surface of an object, i.e., a work and more particularly
for effecting treatment such as film deposition, etching or quality
modification by exposing a work to be treated to a plasma and implanting
ions in the plasma into the work.
2. Description of the Background Art
PSII (Plasma Source Ion Implantation) has been known as a technology for
surface treatment of an object, and an example of an apparatus for the
same is shown in FIG. 6.
This apparatus has a grounded vacuum container 1. An exhaust device 11 and
a treatment gas supply unit 3 are provided for the container 1. The
treatment gas supply unit 3 includes a mass-flow controller, a gas source
and others, which are not shown in the figure. An electrode 2 also serving
as a holder for supporting a work S, i.e., an object to be treated is
arranged in the container 1. The electrode 2 is connected to a DC
high-voltage source 22 through an on-off switch 21. A filament 4 which is
supplied with an electric power and thereby is heated for emitting
electrons is arranged in the container 1. The filament 4 is connected to a
filament power source 41 and a discharge bias power source 42.
For effecting surface treatment on the work S by this apparatus, the work S
is transported into the vacuum container 1 by an unillustrated work
transporting device, and is held by the holder 2. Then, a treatment gas
such as nitrogen gas is supplied into the container 1 from the gas supply
unit 3 while keeping a predetermined degree of vacuum in the container 1
at the order of 10.sup.-4 by operating the exhaust device 11. Also, the
filament power source 41 energizes and thereby heats the filament 4 to
emit electrons, and the discharge bias power source 42 applies a bias
voltage to the filament 4 to accelerate the emitted electrons. Thereby,
the treatment gas which is introduced as described above is ionized to
form plasma P. During this, the electrode 2 is supplied with a negative
high-voltage pulse from the power source 22 through the on-off switch 21.
Thereby, the surface of the work S is exposed to the plasma P, and the
positive ions in the plasma P are accelerated toward the work S and are
implanted into the surface of the work S so that treatment such as
modification of quality is effected on the surface of the work S.
According to the above apparatus and method for the surface treatment,
predetermined treatment can be effected relatively uniformly on the
surface of the work having a complicated three-dimensional structure.
However, the apparatus and method for the surface treatment in the prior
art suffer from the following problems. For example, a work, such as an
object used in semiconductor device, may have different kinds of portions,
i.e., a portion which is covered with an electrically insulating material
or is in a floated potential, and a portion which is made of an
electrically conductive material, such as an electrically conductive
circuit, and it may be desired to effect the treatment only on the above
conductive portion. In the processing for this treatment, a pulse voltage
is not applied to the insulated portion or the portion carrying the
floated potential (both of which will be generally termed as the
"insulated portion"), and the positive ions are not ideally implanted into
the insulated portion. However, due to the weight of ions, the ions cannot
rapidly change their course at the vicinity of the surface of the
insulated portion during an on-period of the pulse voltage so that the
ions collide with and are implanted into the surface of the insulated
portion at and around its end. Generally, when ions are implanted into a
work surface with a high energy from about several kilovolts to hundreds
of kilovolts, a large amount of secondary ions are emitted from the work
surface. If the work surface partially has an insulated portion, positive
electric charges are rapidly accumulated at the surface of the insulated
portion due to the positive ions, which are implanted into the other
portion, i.e., the conductive portion and the end of the insulated
portion, and emitted secondary electrons. As a result, an electric field
formed by the positive charges causes irregularities in the ion
implantation distribution at the conductive portion, and discharge occurs
between the surface of the insulated portion and the surface of the
conductive portion supplied with the negative high-voltage pulse so that
the surface of these portions may be destroyed.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method for surface treatment, in
which predetermined surface treatment can be effected on a work portion
made of an electrically conductive material without damaging the work even
if the work has a surface portion made of an electrically insulating
material or carrying a floated potential as well as an apparatus for
implementing the method.
Another object of the invention is to provide a method for surface
treatment, in which predetermined surface treatment can be effected
uniformly on a work portion made of an electrically conductive material
even if the work has a surface portion made of an electrically insulating
material or carrying a floated potential as well as an apparatus for
implementing the method.
The invention provides a work surface treatment method comprising the steps
of supporting a work by a work support electrode arranged in a vacuum
container; supplying a treatment gas corresponding to intended treatment
of the work into said container; forming plasma from the gas by applying
in a vacuum an amplitude-modulated high-frequency power to an electrode
electrically insulated from said work support electrode, said
amplitude-modulated high-frequency power being prepared by effecting
amplitude modulation on a basic high-frequency power having a
predetermined frequency in a range from 10 MHz to 200 MHz with a
modulation frequency in a range from 1/1000 to 1/10 of said predetermined
frequency; and applying a positive pulse voltage to said work support
electrode to effect the treatment on the surface of said work supported by
said work support electrode.
The invention also provides a work surface treatment apparatus comprising a
vacuum container; a work support electrode arranged in said vacuum
container; an electrode electrically insulated from said work support
electrode; an exhaust device; a treatment gas supply device; a
high-frequency power supply device for supplying an amplitude-modulated
high-frequency power to the electrode electrically insulated from said
work support electrode, said amplitude-modulated high-frequency power
being prepared by effecting amplitude modulation on a basic high-frequency
power having a predetermined frequency in a range from 10 MHz to 200 MHz
with a modulation frequency in a range from 1/1000 to 1/10 of said
predetermined frequency; and a pulse voltage application device for
applying a positive pulse voltage to said work support electrode.
Said amplitude modulation may be pulse modulation performed by on/off of
supply of the electric power, or may be modulation in a pulse form.
Variation with time occurs in density of the negative ions in the plasma
while the plasma is being formed from the gas by supplying the
pulse-modulated high-frequency power.
This variation will now be described below with reference to FIG. 1.
According to the research and study by the inventors, negative ions
present in the plasma, which remains after cut-off of the pulse-modulated
high-frequency power, start to increase in quantity, although this depends
on a magnitude and others of the pulse-modulated high-frequency power. In
this illustrated example, the increase of the negative ions reaches a peak
after about 40 .mu.sec from cut-off of the pulse-modulated high-frequency
power, and the negative ions will disappear within about 200 .mu.sec after
the cut-off of the power. Therefore, the negative ions in the remaining
plasma can be implanted into the work surface in such a manner that the
pulse-modulated high-frequency power is supplied to the treatment gas for
forming the plasma from the treatment gas, and the positive voltage is
applied to the electrode supporting the work during a period containing a
period that a large amount of negative ions are present after the cut-off
of the power. This is owing to the fact that the negative ions are
accelerated toward the work support electrode by a potential difference
between the work support electrode and the plasma formed by application of
the positive voltage.
The work may partially have an insulated portion (a portion made of an
electrically insulating material or a portion in a floated potential) at
its surface. In this case, the negative ions are implanted into an end of
the insulated portion. However, charges of the implanted negative ions and
charges of the emitted secondary electrons cancel each other so that
accumulation of the charges at the work surface can be suppressed to a
practically allowable extent. Thereby, it is possible to suppress the
irregular surface treatment which may be caused by accumulation of charges
as well as damages on the object which may be caused by discharging at the
vicinity of the work surface.
The foregoing and other objects, features, aspects and advantages of the
present invention will become more apparent from the following detailed
description of the present invention when taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a density of negative ions in plasma formed by supply of a
pulse-modulated high-frequency power;
FIG. 2 schematically shows a structure of an example of a work surface
treatment apparatus according to the invention;
FIG. 3 shows at (A) an example of timing of supply of a pulse-modulated
high-frequency power to an electrode 7 during work surface treatment by
the apparatus shown in FIG. 2, shows at (B) an example of timing of
application of a positive pulse voltage to an electrode 2, and shows at
(C) an example of timing of application of a negative pulse to the
electrode 2;
FIG. 4 shows at (A) a specific example of timing of supply of the
pulse-modulated high-frequency power to the electrode 7 during work
surface treatment by the apparatus in FIG. 2, and shows at (B) a specific
example of the timing of supply of the positive pulse voltage to the
electrode 2;
FIG. 5 shows an example of a relationship between the positive pulse
voltage and the adhesion strength of a film formed by the method of the
invention; and
FIG. 6 shows a schematic structure of an example of a work surface
treatment apparatus in the prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A work surface treatment method which will be described below comprises the
steps of supporting a work by a work support electrode arranged in a
vacuum container; supplying a treatment gas corresponding to intended
treatment of the work into the container; forming plasma from the gas by
applying in a vacuum an amplitude-modulated high-frequency power to an
electrode electrically insulated from said work support electrode, said
amplitude-modulated high-frequency power being prepared by effecting
amplitude modulation on a basic high-frequency power having a
predetermined frequency in a range from 10 MHz to 200 MHz with a
modulation frequency in a range from 1/1000 to 1/10 of said predetermined
frequency; and applying a positive pulse voltage to said work support
electrode to effect the treatment on the surface of said work supported by
said work support electrode.
A work surface treatment apparatus which will be described below comprises
a vacuum container; a work support electrode arranged in the vacuum
container; an electrode electrically insulated from the work support
electrode; an exhaust device; a treatment gas supply device; a
high-frequency power supply device for supplying an amplitude-modulated
high-frequency power to the electrode electrically insulated from said
work support electrode, said amplitude-modulated high-frequency power
being prepared by effecting amplitude modulation on a basic high-frequency
power having a predetermined frequency in a range from 10 MHz to 200 MHz
with a modulation frequency in a range from 1/1000 to 1/10 of said
predetermined frequency; and a pulse voltage application device for
applying a positive pulse voltage to said work support electrode.
A preferred embodiment of the invention will now be described below with
reference to the drawings.
FIG. 2 shows a schematic structure of an example of a work surface
treatment apparatus according to the invention. This apparatus has a
vacuum container 1 additionally provided with an exhaust device 11.
Electrodes 2 and 7 opposed to each other are arranged in the container 1.
The electrode 2 serves also as a work support holder, and is connected to
a DC power source 22 through a low-pass filter 20 and an on-off switch 21.
In FIG. 2, the power source 23 and on-off switch 23S will be described
later more in detail. A heater h is provided at the electrode 2. The
electrode 7 is a high-frequency electrode and is connected to a signal
generator 73 which can generate an arbitrary waveform through a matching
box 71 and a high-frequency power source 72. A control unit CONT is
connected to the switch 21 and the high-frequency power source 72, and
controls timing of supply of a pulse-modulated high-frequency power and
application of a positive pulse voltage, which will be described later.
Further, a treatment gas supply unit 3 is provided for the container 1. The
gas supply unit 3 includes one or more gas sources 331, 332, . . . of
treatment gases which are connected to the container 1 through mass-flow
controllers 311, 312, . . . and electromagnetic valves 321, 322, . . . ,
respectively.
For effecting predetermined surface treatment on the work S by this
apparatus, the work S is transported into the container 1 and is held by
the holder 2. Then, the exhaust device 11 operates to attain and keep a
predetermined degree of vacuum in the container 1. Also, a treatment gas
is supplied into the container 1 from the gas supply unit 3, and the
high-frequency power is supplied from the signal generator 73 to the
electrode 7 through the high-frequency power source 72 and the matching
box 71. The high-frequency power thus supplied is prepared by pulse
modulation which is effected on a basic high-frequency power having a
predetermined frequency in a range from 10 MHz to 200 MHz with a
modulation frequency in a range from 1/1000 to 1/10 of the predetermined
frequency of the basic high-frequency power. Also, a positive voltage of a
predetermined magnitude is applied to the electrode 2 from the power
source 22 through the on-off switch 21. The supply of the pulse-modulated
high-frequency power to the electrode 7 and the application of the
positive voltage to the electrode 2 are controlled to start and stop
repetitively at constant periods.
The basic high-frequency power before modulation for producing the
amplitude-modulated high-frequency power may have a sinusoidal waveform, a
square waveform, a saw-tooth-like waveform, a triangular waveform or
others.
By the following reason, the embodiment uses the basic high-frequency power
having the frequency in the range from 10 MHz to 200 MHz. If it were lower
than 10 MHz, it would be difficult to trap or confine efficiently the
plasma. If it were larger than 200 MHz, it would be difficult for
electrons to follow sufficiently the frequency, and it would be difficult
to produce efficiently the plasma.
By the following reason, the embodiment employs the frequency for the
amplitude modulation in the range from 1/1000 to 1/10 of the frequency of
the basic high-frequency power. If it were smaller than 1/1000, it would
be difficult to obtain an effect by the modulation. If it were larger than
1/10, the amplitude modulation would result in a state similar to a state
achieved by double supply of the basic high-frequency power rather than a
state achieved by effecting the amplitude modulation on the basic
high-frequency power.
A duty ratio (on-time/on-time and off-time) of the pulse modulation of the
high-frequency power can be in a range from about 0.1% to about 50%.
The timing at which the modulated high-frequency power is supplied to the
electrode 7 and the positive pulse voltage is applied to the electrode 2
are determined as follows. The timing of rising of the positive pulse
voltage applied to the electrode 2 (application start timing or on-timing)
is determined between an intermediate time (e.g., a half point) in the
on-period of supply of the pulse-modulated high-frequency power to the
electrode 7 and a certain time in the subsequent off-period. The timing of
falling of the positive pulse voltage applied to the electrode 2
(application stop timing or off-timing) is determined between a certain
time in the off-period of supply of the pulse-modulated high-frequency
power to the electrode 7 and an intermediate time (e.g., a half point) in
the subsequent on-period. More preferably, it is determined between the
time in the off-period of supply of the pulse-modulated high-frequency
power supply to the electrode 7 and the end of this off-period.
Further, the period for which the positive pulse voltage is applied to the
electrode 2 preferably includes a period during which negative ions are
present after cut-off of the pulse-modulated high-frequency power to the
electrode 7, and further preferably includes a portion or the whole of the
period during which many negative ions are present. The foregoing timing
in connection with application of the positive pulse voltage is an example
of the timing determined within the period including at least a portion of
the period during which many negative ions are present. In contrast to
this example, it is not impossible to apply the positive pulse voltage
during the whole period of the treatment. However, if the on-period of
application of the positive pulse voltage is excessively larger, a power
supply cost wastefully and therefore unpreferably increases.
From the foregoing, it can be understood that the application of the
positive pulse voltage is preferably performed at least for a period
starting before and ending after the point of time when the quantity of
the negative ions reaches the peak during the off-period of the
pulse-modulated high-frequency power.
A specific example is as follows. As shown at (A) and (B) in FIG. 3, the
supply of the high-frequency power to the electrode 7 stops at the same
timing as the start of application of the positive voltage to the
electrode 2, and the application of the positive voltage to the electrode
2 stops during the off-period of supply of the high-frequency power to the
electrode 7.
Thereby, treatment depending on the kind of the treatment gas is effected
on the surface of the work surface S.
According to the work surface treatment method and apparatus described
above, the negative ions in the plasma increase in quantity after the stop
of supply of the pulse-modulated high-frequency power to the electrode 7.
However, the positive voltage is applied to the work support electrode 2
during the period containing the above period so that the increased
negative ions in the plasma can be implanted into the work surface S. This
is owing to the fact that the negative ions are accelerated toward the
electrode 2 by the potential difference between the electrode 2 and the
plasma P during the period of the application of the positive voltage to
the electrode 2. The work S may partially have an insulated portion (a
portion made of an electrically insulating material or a portion in a
floated potential) at its surface. In this case, the negative ions are
also implanted into a portion of the insulated portion. However, charges
of the implanted negative ions and charges of the emitted secondary
electrons cancel each other so that accumulation of the charges at the
work surface S can be suppressed to a practically allowable extent.
Thereby, it is possible to suppress the irregular surface treatment of the
work S which may be caused by accumulation of the charges as well as
damages of the work S which may be caused by discharging at the vicinity
of the work surface S.
The positive pulse voltage applied to the electrode 2 is in a range from 50
V to 300 kV. If it were lower than 50 V, the ions implanted into the work
would have an excessively low energy so that the ion implantation would
not achieve an intended effect. If it were higher than 300 kV, the
discharge current would excessively increase so that the thermal damage
applied to the work would impractically increase. The magnitude of the
positive pulse voltage is appropriately determined within the above range
in accordance with the specific treatment to be effected. When the ions
are to be implanted into a portion at a small depth from the surface of
the work, the positive pulse voltage is set in a range from 50 volts to
several kilovolts. If the ions are to be implanted into a comparatively
deep portion, the voltage is set in a range from several kilovolts to 300
kilovolts.
As another example for implementing the method of the invention by the
apparatus shown in FIG. 2, such a manner may be employed that the plasma
is formed from the treatment gas by supplying the pulse-modulated
high-frequency power to the electrode 7 similarly to the foregoing
embodiment, and the positive pulse voltage is applied to the electrode 2
at the predetermined timing. Also, the negative pulse voltage is applied
to the electrode 2 from the DC power source 23 through the switch 23S (see
FIG. 2) during an off-period of application of the positive pulse voltage
to the electrode 2.
The switch 23S is controlled by the control unit CONT. The DC power source
23 for applying the negative pulse voltage may commonly use a portion of
the DC power source 22 for applying the positive pulse voltage.
The period for applying the negative pulse voltage to the electrode 2 may
be the same as a portion or the whole of the off-period of application of
the positive pulse voltage to the electrode 2. For example, as shown at
(C) in FIG. 3, the negative pulse voltage is applied from the DC power
source 23 during the same period as the on-period of supply of the
pulse-modulated high-frequency power to the electrode 7. This improves the
speed of treating the work S. Even when the negative pulse voltage is
applied in the above manner, accumulation of the positive charges at the
surface of the insulated portion can be suppressed to an allowable extent
by applying the positive pulse voltage during a period other than the
above.
As exemplified in FIG. 4, the application of the positive pulse voltage to
the electrode 2 from the power source 22 may be performed during a period
containing a period within the off-period of supply of the high-frequency
power to the electrode 7 and particularly during a period in which the
quantity of negative ions is large (preferably, a period starting before
and ending after the peak of the quantity of the negative ions).
As an example of the work surface treatment apparatus of the preferred
embodiment of the invention, description has been given on the treatment
apparatus of the capacity-coupling type in which the electrode 7
electrically insulated from the work support electrode 2 supplied with the
modulated high-frequency power is arranged in the vacuum container 1 (see
FIG. 2). However, such a treatment apparatus of an induction-coupling type
may be employed that an electrode electrically insulated from the work
support electrode supplied with the modulated high-frequency power is
wound around the vacuum container.
According to the invention, when a high-frequency power is supplied, a
magnetic field may be formed, thereby a helicon wave plasma can be formed.
According to the invention, when the treatment gas is a deposition gas, a
film can be deposited on the work. Also, etching can be performed with an
etching gas, and modification of a surface quality can be performed with a
surface quality modification gas.
A specific example will now be described below. In this example, the
apparatus in FIG. 2 was used. The pulse-modulated high-frequency power and
the positive pulse voltage were supplied to the electrodes 7 and 2 in
accordance with patterns shown at (A) and (B) in FIG. 4, respectively.
According to the pattern of supply of the pulse-modulated high-frequency
power shown at (A) in FIG. 4, the on-time was 1.25 .mu.sec, the off-time
was 23.75 .mu.sec and the duty ratio was 5%. As shown at (B) in FIG. 4,
the positive pulse voltage rose after 8 .mu.sec from cut-off of the
pulse-modulated high-frequency power, and fell down elapsing of 10 .mu.sec
after the rising. A work was made of stainless steel but had a portion
electrically insulated by plastics. By the treatment, a titanium nitride
film was deposited on a surface of the portion made of the stainless steel
of the work.
Specifications of the Apparatus
Size of high-frequency electrode 7: 270 mm in diameter
Size of work support electrode 2: 300 mm in diameter
Distance between electrodes: 30 mm
Conditions for Deposition
Work S: a work made of stainless steel and having a portion made of
plastics (The portion of stainless steel had a length of 150 mm, a width
of 16 mm and a thickness of 10 mm.)
Pulse-modulated high-frequency power:
Basic high-frequency power:
frequency: 13.56 MHz
200 W
Pulse modulation frequency: 40 kHz
Duty ratio: 5%
Positive pulse voltage: 5 kV
frequency: 40 kHz
on-time: 10 .mu.sec
off-time: 15 .mu.sec
Deposition gas:
TiCl.sub.4 16 sccm (tank temperature: 50.degree. C.)
N.sub.2 10 sccm
Deposition pressure: 0.1 Torr
Deposition time: 5 minutes
Any discharge scratch or damage was not found at the surface of the
titanium nitride film obtained in this above example.
A pulling jig or member having a columnar form of 8 mm in diameter was
adhered by adhesive onto the surface of the titanium nitride film
deposited in this above example, and a force required for separating the
pulling jig from the surface was measured for evaluating the film adhesion
strength. As a result, it was found that the film adhesion strength was 20
times or more larger than that of a titanium nitride film formed by a
conventional plasma CVD method. It can be consider that the high film
adhesion strength was achieved owing to implantation of the negative ions
in the plasma into the work S in addition to the effect by the
conventional plasma CVD.
FIG. 5 shows relative values of the film adhesion strength with various
magnitudes of the positive pulse voltage applied to the electrode 2 from
100 V to 1000 kV. It can be seen from FIG. 5 that the film adhesion
strength increases with the positive pulse voltage.
Although the present invention has been described and illustrated in
detail, it is clearly understood that the same is by way of illustration
and example only and is not to be taken by way of limitation, the spirit
and scope of the present invention being limited only by the terms of the
appended claims.
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